Chlamydia pneumoniae is the new third species of genus Chlamydia with one strain (serovar) called TWAR. It is proposed to investigate the epidemiology of several aspects of TWAR infection now poorly understood and shown to be of potential importance. These are TWAR infections in the elderly, in children in the tropics, during military training, in relation to asthma, and in coronary artery disease and other atherosclerosis. The technique used for these studies include microimmunofluorescence serology, isolation of the organism in HL cell culture and the polymerase chain reaction (PCR) to demonstrate TWAR specific DNA. The pathology and microbiology of TWAR infection in the lung will be studied in both human lung and with an experimental mouse model of pulmonary infection. The human lungs to be studied will include tissue from autopsies, both fresh and archival, and bronchioaleveolar lavage and bronchial brushing specimens from bronchoscopy. Latent and relapse infection will be sought. The techniques for these studies of lungs include those listed above, plus immunochemical staining of tissue sections utilizing TWAR specific monoclonal antibody (human tissue only), double-label immunofluorescent antibody stain, and in situ hybridization. Antibiotic treatment of C. pneumoniae infection, particularly directed at eradication of the organism from tissue, will be studied in the mouse model of TWAR pneumonia. A major thrust of the project is to identify, isolate, and produce specific antigens of C. pneumoniae using recombinant and synthetic techniques. Such antigens will be applied to simplified serology and development of vaccine for prevention of infection. The mouse model will be used for studies of prevention by immunization. The epidemiological studies will identify populations that can benefit from immunization.